1. Field of the Invention
The present invention relates to a method for producing a developing agent for developing an electrostatic image or a magnetic latent image in electrophotography, an electrostatic printing method, a magnetic recording method or the like, and particularly relates to a technique for obtaining toner particles by aggregating particles of developing agent materials.
2. Description of the Related Art
In the past, as a method for producing a toner in which the shape and surface composition of toner particles are intentionally controlled, for example, as disclosed in JP-A-63-282752, JP-A-6-250439 and JP-A-9-311502, an aggregation method in which particles containing a binder resin and a coloring agent are aggregated and fused has been proposed, and in a step of preparing a dispersion of particles containing a binder resin and a coloring agent, a method for producing particles by a polymerization method such as emulsion polymerization or suspension polymerization, a phase inversion emulsification method using an organic solvent or applying a mechanical shearing force, or the like can be employed.
When toner particles are produced by aggregating and fusing particles of toner materials, evaluation of a dispersion prior to aggregation was carried out by measuring particle size distribution of a resulting toner using a laser scattering/diffraction type particle size analyzer or a centrifugal sedimentation type particle size analyzer, and regulating the uniformity of particle size distribution.
However, according to this method, although it is possible to confirm the distribution of particles having a small particle size which occupy the most part in the dispersion, it is difficult to measure coarse particles, which do not exist so much, and it is impossible to quantitatively measure the number of coarse particles. When a large amount of coarse particles exist, particles composed of only a non-colored resin exist, and tinting of a toner is not sufficient, resulting in problems such as liberation of a coloring agent due to non-formation of aggregated particles together with resin particles, deterioration of charge properties due to exposure of a coloring agent on the toner surface and deterioration of OHP transmittance of toner due to the coarse particles as disclosed in JP-A-10-301333. Also, a releasing agent is exposed on the surface of toner particles and thus the fixability of toner is deteriorated, resulting in a problem that the OHP transmittance is reduced due to irregular reflection.